Direct upload

Upload flow

1. Request an upload session for the published form and intended files.
2. Upload bytes directly to private storage using the authorized method.
3. Finalize the session and receive file identifiers.
4. Submit those identifiers with the form fields.

Send identifiers, not base64

Large base64 payloads inflate requests and bypass the resumable flow. Use the file identifiers bound to the form and upload session.

Test interrupted uploads

Pause, resume, expire, cancel, and delete synthetic files before depending on the path for production attachments.